FR2648617A1 - FLUORESCENT LAMP - Google Patents

Abstract

In a fluorescent lamp, a curved discharge path consists of several bulbs 1a, 1b and a base 10 interconnecting end parts of the bulbs. End electrodes 4a, 4b are provided at the end portions of the ampoules which are located at both ends of the discharge path. An intermediate electrode 12 is arranged inside the base. A voltage is selectively applied between the intermediate electrode 12 and the terminal electrodes 4a, 4b, so that the bulbs can be selectively allowed to emit light. The bulbs have openings 3a, 3b having different widths and positions. Layers of phosphor substance of different types 2a, 2b are formed on the internal faces of the bulbs, so that there is selective emission of lights of different wavelengths.

Description

2648 6 1 7

  The present invention relates generally to a fluorescent lamp having a curved discharge path, for example a U-shaped path or a W-shaped path, and, more particularly, a fluorescent lamp having several bulbs, the ends of which are connected at a base, where the bulbs and the base form a U, S or W path. A fluorescent lamp is used not only as a source for the general lighting of the premises, but also as a source

  special lighting in various applications.

  For example, a fluorescent lamp is used for "rear lighting" in a display device with

  liquid crystal, the lamp illuminating the rear surface of the device

  tif display. In addition, the lamp is used as a light source in a copying machine, or for other lighting

special.

  When using the fluorescent lamp for lighting

  back of the liquid crystal display, it is necessary

  Make sure that the lamp illuminates the rear face of the display unit almost uniformly. For this purpose, a number of fluorescent lamps with a straight bulb are arranged in parallel, or else a fluorescent lamp is used which has a U-shaped or W-shaped bulb. When many fluorescent lamps with a straight bulb are juxtaposed , many sockets and many supports

  lamps are required and complex wiring is required.

  Under these conditions, fluorescent lamps are widely used having U-shaped, S-shaped or W-shaped bulbs. So, using a single lamp, one can light

uniformly a large area.

  While the use of this unique fluorescent lamp

  curved bulb resistor reduces the number of sockets and simplifies wiring, it is difficult to make a bulb

having this complicated shape.

  On the other hand, there is known a fluorescent lamp of the so-called opening type which can be used for lighting from the rear of a liquid crystal display device. When we

26486 1 7

  uses a fluorescent lamp for rear lighting, it is not necessary for the bulb of the lamp to emit light over its entire peripheral area. It suffices that the light is emitted by only a given part of its periphery. Taking this into account, the aperture-type fluorescent lamp is given a slit-like opening extending continuously, in the axial direction of the bulb of the lamp. No phosphor is deposited on the part of the bulb which corresponds to the opening. A reflective deposited layer is formed on the part of the external surface of the bulb which corresponds to the

  remaining internal surface of the bulb carrying the luminous substance

  phore. In the aperture type fluorescent bulb, the light emitted from the part coated with the phosphor substance is reflected by the reflective deposited layer, and most of the light radiates, via the aperture, in an interval

  predetermined only from the circumference. Thus, the fluorescent lamp

  opening type can efficiently emit heat

  light towards the only surface asking to be lit.

  An aperture type fluorescent lamp having a curved bulb is manufactured in the following manner. All

  first, we prepare a straight bulb. We put on a

  tance phosphor the inner surface of the bulb, except the surface of a slit-shaped opening, and a

  reflective layer on the outer surface of the corresponding bulb

  laying on the internal surface coated with phosphor substance. The bulb thus designed is heated and it is partially curved into a U shape or a W shape.

  When using the open type fluorescent lamp

  ture as a means of lighting from the back of a liquid crystal display, it is necessary in some cases to vary the axial length of the opening or to modify the position of the opening in the circumferential direction of the bulb, for uniform illumination. However, in the case of a fluorescent lamp with a curved bulb, it is difficult to vary the length of the opening and, or else, to modify the circumferential position of the opening over the entire axis of the bulb. When several fluorescent lamps having rectilinear bulbs are arranged in parallel, as above indicated, it is possible to switch on only some of them to modify the quantity of light and, or else, the distribution

  of light intensity. However, in the case of the fluorescent lamp

  with the curved bulb, it is not possible to

  only light part of the bulb.

  In the case where a fluorescent lamp is used as a light source in a copying machine, it is necessary in certain cases to vary the wavelength of the Light according to the hue, etc., of the original to be reproduced. In a lighting device where several fluorescent lamps are arranged in parallel, it is possible to place fluorescent lamps capable of emitting light according to various wavelengths and to selectively switch them on in order to modify the wavelength of the light emitted. This is however

  not possible in the case of a fluorescent lamp with a curved bulb.

  In addition, in the case of the fluorescent lamp with a curved bulb, the positive column produced in the bulb shifts from the center of the straight section of the bulb towards the side.

  internal part of the curved part. As a result, a non-uniform light

  form is emitted by the curved part of the bulb.

  The aim of the present invention is to solve the problems

  above mentioned problems for a fluorescent lamp having a

curved bulb.

  To achieve this goal, in this invention, we have

  substantially parallel several substantially straight bulbs

  lines. The terminal parts of the bulbs are connected using a base. A curved discharge path goes through the bulbs and

the nerve.

  With this structure, a discharge path, or bulb,

  curved can be made using simple operations.

  According to preferred embodiments of the invention,

  you can easily change the width and circumferential position

  tial of the opening formed in each bulb, and we distribute and

  freely adjusts the light emitted.

  In addition, there is provided inside the base an electric

  intermediate electrode, and a voltage is selectively applied between the intermediate electrode and terminal electrodes, so as to cause an electric discharge to take place selectively in the bulbs and to selectively allow the bulbs

to emit light.

  In addition, it is arranged that the layers of phosphor coating deposited on the internal surfaces of the bulbs are of mutually different types, so that the layers of phosphor coating can emit tumors of lengths.

different wave.

  In addition, an element is provided in a connection part.

  between the bulbs and the base, communication openings

  tion are formed in the Element to allow the interior of the bulbs to communicate with the interior of the base, and each communication orifice is moved away from the center, or center of gravity, of the cross section of each bulb towards the outside the curved area of the discharge path. Thus, one can compensate for the displacement of the positive column inwards in the curved zone and one maintains the positive column in the center of each

bulb.-

  The following description, intended as an illustration of

  the invention aims to give a better understanding of its characteristics and advantages; it is based on the appended drawings, among which: FIG. 1 is a side view of an aperture type fluorescent lamp having a U-shaped discharge path, according to a first embodiment of the invention; Figure 2 is an exploded vertical cross-sectional view of the fluorescent lamp shown in Figure 1; Figure 3 is a cross-sectional view taken along line 3-3 of Figure 1;

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  Figure 4 is a side view of an aperture type fluorescent lamp having an S-shaped discharge path, according to a second embodiment of the present invention; Figure 5 is an exploded vertical cross-sectional view of the fluorescent lamp shown in Figure 4; Figure 6 is a cross-sectional view taken along line 6-6 of Figure 4; Figure 7 is a cross-sectional view of bulbs having openings of different widths;

  Figures 8 and 9 are cross-sectional views

  bulb versals, having various arrangements of phosphor layers and reflective layers;

  Figure 10 is a side view of a fluorescent lamp

  resent having an S-shaped discharge path, according to a third embodiment of the invention, where the types of phosphors are varied; Figure 11 is an exploded vertical cross-sectional view of the fluorescent lamp of Figure 10; Figures 12A and 12B are cross-sectional views taken along line 12-12 of Figure 10;

  Figure 13 is a perspective view of a fluorescent lamp

  resente with bulbs each having an oval cross section, according to a fourth embodiment of the invention; Figure 14 is a front view of the base portion of Figure 14; and FIG. 15 is a perspective view illustrating an apparatus which makes it possible for example to manufacture the fluorescent lamp

in Figure 13.

  We will now describe embodiments pre-

  invented. Figures 1 to 3 show an aperture type fluorescent lamp having a discharge tube in

  U shape according to a first embodiment of the invention.

  Layers of phosphor substance 2a and 2b are deposited on the internal surface of the light emitting bulbs 1a and 1b. In this embodiment, the bulbs 1a and 1b are

of the rectilinear type.

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  The phosphor layers 2a and 2b can

  be made of the same material. For example, a lumino-

  well-known three-wavelength phore, which is produced by mixing phosphors of the three primary colors, blue (B), green (G) and red (R), is used. Alternatively, the phosphor layers 2a and 2b can be formed by phosphors of different colors. For example, the layer of phosphor substance 2a is formed by one of the blue, green and red phosphors, and the layer of substance

  phosphor 2b is formed by others.

  A predetermined area of the internal surface of each

  bulb 1a and 1b, extending in its circumferential direction

  tial, is not coated with the phosphor layer 2a, 2b. This area acts as an opening, or part of the light transmission slot, 3a, 3b, on which the glass surface is exposed. The light transmission slot part 3a, 3b extends over a predetermined distance along the axis of the bulb 1a, 1b. Thus, the bulbs 1a and 1b have slot light transmission slots 3a and 3b which extend axially. In this embodiment, the lengths of the slit parts 3a and 3b are equal, but the slit parts 3a and 3b are located in

opposite directions.

  The slit parts 3a and 3b constitute transparent parts of the glass bulbs. Thus, when the bulbs are turned on, the slit portions 3a and 3b have a luminance which is 1.3 to 1.5 times greater than that of the region of the phosphor layers 2a and 2b. A large amount of light is emitted from the light transmitting slot parts 3a and 3b,

  and the bulbs have a certain directivity.

  The light emitting bulbs 1a and 1b have, at their first ends, terminal electrodes 4a and 4b (hot cathodes in this embodiment). In each of the bulbs 1a and 1b, the ends of a filament 5 are connected to conductive wires 6. The wires 6 penetrate, under hermetic conditions, into a rod, or queusot, 7. The rod 7 is welded to a part open terminal of bulb 1a, 1b.

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  Thus, the first ends of the bulbs la and lb

  are hermetically closed by the terminal electrode 4a, 4b.

  The second terminal parts of the emission bulbs

  light 1a and 1b are connected to each other by means of

  diary of a coupling device 8. The coupling device 8 comprises for example a sealing plate 9 and a base 10. The

  sealing plate 9 is formed for example of an insulating material.

  The sealing plate 9 has communication openings 9a and 9b which communicate with the openings present at the second ends of the ampoules 1a and 1b. The insulating sealing plate 9

  is hermetically connected to the openings present at the two

  tenth ends of the bulbs la and lb via a

adhesive (not shown).

  The base 10 is formed for example by an electric material

  triconductive and not allowing light to pass through. The

  base 10 is mounted on the sealing plate 9 and is hermetic-

  ment coupled to it by means of an adhesive (not shown

  felt). The space defined by the sealing plate 9 and the base

  10 is allowed to communicate with the bulbs la and lb via the ori-

  communication ports 9a and 9b formed in the sealing plate 9. Thus, the ampoules 1a and 1b and the coupling device 8 constitute, in one piece, a discharge path in the form of

U, designated by reference 11.

  The communication orifice 9a, 9b is spaced from the center of the straight section of the bulb la, lb, that is to say the center of gravity of the straight section of the bulb la, lb, by a predetermined distance to the outside in the curved region

  of the discharge path 11. This displacement of the communication orifice

  tion 9a, 9b outwards compensates for the tendency of the positive column to move inwards in the curved region of the discharge path 11, which makes it possible to maintain the position of the positive column in the center of the bulb. We will explain the reason for this. Generally, the positive column tends to remain at the center of the cross section, or center of gravity of the cross section, of the discharge path. So if we move the orifice of

2648 6 17

  communication 9a, 9b to the outside of the curved region of

  the bulb, the positive column which passes through the communication orifice

  cation 9a, 9b tends to be located in the center of the communication orifice

  cation, i.e. outward from the curved region. This tendency towards an outward displacement compensates for the tendency towards an inward displacement of the positive column in the curved region of the discharge path. As a result, the positive column is held in the center of the discharge path 11, and therefore almost in the center of the bulb 1a, 1b. The degree of displacement of the communication orifice 9a, 9b towards the outside is determined according to the diameter of the communication orifice 9a, 9b, the shape of the curved region, and other characteristics of the fluorescent lamp. . It is possible to obtain, by means of calculations or experiments, the optimal value of the displacement of the communication orifice 9a, 9b

outwards.

  An intermediate electrode 12 serving as the third electrode is placed inside the space defined by the sealing plate 9 and the base 10. The intermediate electrode 12 is constituted so that wires 14 are connected to the two ends d 'a filament 13 and penetrate hermetically into the base 10. The wires 14 extend to the outside of the base 10. Naturally, the wires 14 are electrically insulated from each other

pellet 10.

  A predetermined quantity of mercury and a rare priming gas is hermetically sealed in the U-shaped discharge tube 11 constituted by the bulbs la and lb and the device

coupling 8.

  In this fluorescent lamp, when the terminal electrodes 4a and 4b which are connected to the two ends of the discharge path 11 receive an electrical supply, an electrical discharge is caused to occur between the terminal electrodes 4a and 4b. The electrical discharge occurs along the entire length of the U-shaped discharge path 11; so from La

  light is emitted from the entire U-shaped discharge path 11.

2648 6 17

  However, in the present embodiment, the base is formed by a material which does not transmit light and, therefore, the base 10 does not emit light. So the Light

  is emitted simultaneously by the bulbs 1a and 1b juxtaposed.

  The bulbs 1a and 1b emit light, as a result of the light emission of the phosphor layers 2a and 2b. A predetermined circumferential part of the bulb 1a, 1b is provided with a slot for transmitting light 3a, 3b, on which no phosphor substance is deposited. The slit part 3a, 3b has a luminance of 1.3 to 1.5 times greater than that of the layer of luminophore substance 2a, 2b. Consequently, more light is emitted from the slit portions 3a and 3b. In the embodiment, since the parts

  light transmission slots 3a and 3b are located vertically-

  in opposite directions, the lamp emits a greater amount of light upwards and the lamp lb emits more

  large amount of light down.

  For example, when the layers of phosphor

  2a and 2b capable of emitting lights of different colors

  annuities are formed on the internal surfaces of the light emitting lamps 1a and 1b, the amount of light emitted upwards differs from that emitted downwards. Thus, the color of the light emitted upwards differs from that of the light emitted downwards.

  On the other hand, when applying electrical power

  at the intermediate electrode 12 and at one of the terminal electrodes 4a and 4b placed at the two ends of the discharge path 11, for example the electrode 4a, an electric discharge occurs between the electrodes 4a and 12. Consequently, only one of the bulbs, the, of the U-shaped discharge path 11 is

  allowed to emit light.

  In this case, the length of the discharge path 11 over

  which of the light is emitted is substantially halved.

  Thus, the light-emitting surface decreases and the amount of light emitted is almost halved. It is thus possible

  to illuminate a particular part of an object.

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  In addition, in this case, the bulb having the upward directed light transmitting slit portion 3a can emit light mainly upward. The bulb emits Light having the color corresponding to the layer of phosphor substance 2a which is formed on the internal surface of

the light bulb.

  When the power supply is applied to the intermediate electrode 12 and to the other terminal electrode 4b, the electric discharge occurs between these electrodes 12 and 4b and only the bulb 1b emits light. Since the bulb 1b has its light transmitting slot part 3b which is directed downwards, it emits the light mainly downwards. The bulb 1b emits light having the color corresponding to the layer of phosphor substance 2b formed on the internal surface of the bulb 1b. According to the first embodiment of the invention, there is produced a single fluorescent lamp of the aperture type, in which slot parts of light transmission 3a and 3b are located in opposite directions. Since the emission bulbs

  light 1a and 1b are connected via the device

  tif coupling 8 so as to form the U-shaped discharge path 11, straight tubes can be used for the light emitting bulbs la and lb, and one can omit the bending operation involving a softening by heat. Thus, this prevents degradation of the phosphor by heat, variation in the wall thickness of the bulb, and the

  decrease in mechanical resistance of the bulb.

  It is possible to freely determine the slot part 3a, 3b by rotating the rectilinear bulb 1a, 1b on its axis. In addition, it is possible to prevent the position of the

  slot part 3a, 3b does not vary from one lamp to another.

  By selectively applying electrical power to the terminal electrodes 4a and 4b and to the intermediate electrode 12, the region in which the electrical discharge is caused to occur can be varied. So we can vary the

  Light emission region and the amount of light emitted.

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  By comparison with the case where a certain number of independent lamps is used, it is noted that the number of electrodes decreases as well as that of the sockets and lamp supports. In addition, the

wiring is simplified.

  We will now describe a second embodiment

  of the invention in relation to Figures 4 to 6.

  The fluorescent lamp according to the second embodiment

  tion of the invention employs three rectilinear light emitting bulbs la, lb, lc corresponding to the three primary colors, blue (B), green (G) and red (R). Layers of substance

  phosphor 2a, 2b and 2c formed on the internal surfaces respec-

  tives of the bulbs la, lb and lc can respectively emit a blue-based light whose peak wavelength is for example 453 nm, a green-based light whose peak wavelength is example at 543 nm, and a light based on red whose peak wavelength is for example

at 611 nm.

  The light emitting bulbs 1a, 1b and 1c have slit-shaped light transmitting portions 3a, 3b and 3c which extend in the axial direction of the bulbs and are not coated with the layers of phosphor 2a, 2b and 2c. In this embodiment, the slit parts 3a, 3b and 3c have the same width, but they are located in different directions. The slit part 3a looks towards the upper left side, the slit part 3b upwards, and the

  slot part 3c towards the upper right side.

  The terminal parts of the central bulb lb and of the third bulb lc are connected by a coupling device 18 having the same structure as the coupling device 8 (used to connect the bulbs la and lb in the first mode of

  production). An intermediate electrode 19 is enclosed hermetically sealed.

  only in the coupling device 18.

  The rectilinear light-emitting bulbs 1a, 1b and 1c and the two coupling devices 8 and 18 constitute, in one piece, a substantially N-shaped discharge path

designated by reference 11.

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  When an electrical supply is applied to the terminal electrodes 4a and 4b which are placed at the two ends of the discharge path 11, an electric discharge is caused to occur between the terminal electrodes 4a and 4b. Since the electrical discharge takes place along the entire length of the N-shaped discharge path 11, light is emitted from all of the

  N-shaped discharge path 11.

  In this case, since the layers of phosphor substance

  2a, 2b and 2c of all the bulbs la, lb and lc emit simultaneously

  light, there is simultaneous emission of blue light,

  of green light, of red light.

  The light emission bulbs la, lb and lc com-

  bear slit-shaped light transmitting parts

  bands 3a, 3b and 3c which extend along the axes of the bulbs.

  Since the slit portions 3a, 3b and 3c are located in different directions, for example in the upper left direction, upward and in the upper right direction, light is emitted in the directions of the slit portions 3a, 3b and 3c.

  On the other hand, when applying an electrical supply

  stick at the terminal electrode 4a, placed at one end of the discharge path 11 and at the intermediate electrode 19, an electric discharge takes place between the electrodes 4a and 19. Thus, the electric discharge occurs in the bulbs la and lb , and the phosphor layers 2a and 2b simultaneously emit light. So there is emission of blue light and light

green, for example.

  In this case, depending on the positions of the light transmitting slit portions 3a and 3b of the bulbs 1a and 1b, the light is emitted mainly in the upper direction

left and up.

  When applying electrical power to the terminal electrode 4b, placed at the other end of the path of

  discharge 11, and at the intermediate electrode 12, an electric discharge

  trique takes place between the electrodes 4b and 12. Thus, the electric discharge takes place in the bulbs lb and 1c and the layers of

264B617

  phosphor substance 2b and 2c simultaneously emit

  light. Depending on the positions of the transmission slot parts-

  Light 3b and 3c, light is mainly emitted to

  up and in the upper right direction.

  When applying electrical power to the electric

  terminal trode 4a and at the intermediate electrode 12, the electrical discharge takes place between the electrodes 4a and 12 and only the phosphor layer 2a of the bulb emits light. By

  Therefore, there is emission of blue light, for example, mainly

  payment in the upper left direction via the slot part 3a. When an electrical supply is applied to the intermediate electrodes 12 and 19, electric charges occur between these electrodes 12 and 19, and only the phosphor layer 2b of the bulb 1b emits light. So there is emission of green light, for example, mainly upwards

via the slot part 3b.

  When applying electrical power to the electric

  terminal trode 4b and at the intermediate electrode 19, the electric discharge occurs between these electrodes 4b and 19 and only the phosphor layer 2c of the bulb lc emits light. Therefore, there is emission of red light, for example, mainly in the upper right direction via the

  light transmission slot part 3c.

  As described above, with the second embodiment

  tion, there is a sixfold choice regarding the length of the part of the bulbs on which the electric discharge takes place, and the region of the part of the bulbs in which the light is emitted. In addition, the color of the light emitted obeys a sixfold choice, and one can choose the direction of the light emitted.

  In the first and second embodiments below

  Above described, the position or the direction of the light-transmitting slot parts 1a, 1b and 1c varied according to the respective bulbs; however, these positions or directions can be

  identical in the respective bulbs.

  As shown in FIG. 7, the light-transmitting slit portions 3a and 3b of the bulbs 1a and 1b may have openings of different widths W1 and W2. In that case,

  for example, we can make the S distribution of light uniform

nance on the illuminated surface A.

  When the light transmitting slit part, or the opening part, is formed in the fluorescent lamp, a light transmitting part can be formed, as indicated above.

  light in single glass which is not coated with luminous substance

  phore. According to another possibility, as shown in FIG. 8, it is possible to form a light-shielding layer, or reflective layer, on the internal surface of the bulb 1. In this case, there remains a transmission part. of light in single glass, on which there is no layer

  reflective 30. Next, a layer of luminous substance is deposited

  nophore 31 on the reflective layer 30. The area where it is not

  formed of reflective layer 30 serves as a transmission slot part

light 32.

  In addition, as shown in Figure 9, the light shielding layer, or reflective layer, can be formed.

  on the outer face of the bulb 1, the slot slot of transmission-

  light sion 32 being left.

  In the embodiments presented above, the light-emitting bulb was formed by connections of rectilinear bulbs. However, according to the present invention, it is possible to connect several U-shaped light emitting bulbs. In the embodiments presented above, each of the electrodes was a hot cathode; however, each electrode may be a cold cathode formed from a nickel plate. In the case of a fluorescent lamp having cold cathodes, if the bases 10 of the coupling devices 8 and 18 are formed of an electrically conductive material, it is

  also possible to use the caps 10 as inter-electrode

mediaries.

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  Furthermore, the present invention is not limited to a fluorescent lamp in which mercury is hermetically sealed. This invention can be applied to a rare gas discharge lamp, and hermetically containing xenon, neon or

krypton.

  In Figures 10 to 12B, a third is shown

  embodiment of the invention. The third embodiment

  tion refers to a fluorescent lamp with no openings. Apart from this absence of openings, the structure of the third embodiment is identical to that of the second

  embodiment of FIGS. 4 to 6. In the third,

  sation, the phosphor layers 2a, 2b and 2c present

  te on the internal faces of the bulbs la, lb and lc are of mutually different types. By selecting the layers of phosphor substance, it is possible to cause the lamp to emit lights having

different wavelengths.

  It is possible to arrange the bulbs 1a, 1b and 1c linearly in the same fictitious plan, as shown in FIG. 12A, or else these may not be in this

  plan, as shown in Figure 128. In the case of the provision-

  sition of Figure 12B, it is possible to vary the distance between the illuminated surface A and each bulb. If the distance between the surface A and the central bulb lb is given a greater value than that separating the surface A from the bulbs la and lc, the surface A can be uniformly illuminated. FIGS. 13 and 14 show a fluorescent lamp according to a fourth embodiment of the invention. The structure of the fourth embodiment is identical to that of the first

  embodiment, shown in Figure 1, except that the sec-

  tion right of each of the bulbs la and lb is oval, that no opening is formed there, and that the communication orifices 9a and 9b have a particular structure. According to the fourth embodiment, since the cross section of the bulb 1a, 1b is oval, the area lying opposite the illuminated surface is large, and the illumination can be carried out with high efficiency

and uniform luminance.

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  In the case where the bulb 1a, 1b has a cross section

  right oval, moving the positive column inward

  laughing in the curved area of the discharge path 11 is very important. Therefore, in the fourth embodiment, a cylindrical member 9d, 9e is provided to surround the discharge port 9a, 9b so that the discharge port 9a, 9b can exert a greater displacement compensation effect. of the

positive column.

  Figure 15 illustrates an apparatus and method for

  so much to manufacture the fluorescent lamp described above. The bulbs 1a and 1b and the caps 10 and 19 are connected by means of glass frit, or the like. In this case, we interpose between the

  bulbs and sockets a coupling material in glass frit.

  The bulbs and the caps are maintained in a predetermined position using an appropriate template. The end parts of the caps and the bulbs are placed in a high frequency heating coil 30, as shown in FIG. 15. The high frequency heating coil is exited so as to heat the metal caps, so that one connects the caps and

light bulbs.

  Of course, those skilled in the art will be able to imagine,

  from the devices whose description has just been given to

  title merely illustrative and not limiting, various

* variants and modifications not departing from the scope of the invention.

Claims (8)

  1. Fluorescent lamp having a curved discharge path, characterized in that it comprises: - several tubular bulbs (la, lb, lc) each having a predetermined shape, which serve to form part of said discharge path, the bulbs being arranged so as to have a predetermined positional relationship, each bulb comprising a layer of phosphor coating (2a, 2b, 2c); - at least one base (10) forming part of the discharge path, said base connecting between them the terminal parts of adjacent bulbs and constituting, in combination with said bulbs (la, lb, lc), the curved discharge path ( 11); and - terminal electrodes (4a, 4b), which are placed at the terminal parts of the bulbs which are at the two ends of said discharge path (11).   2. Fluorescent lamp according to claim 1, character-   in that an intermediate electrode (12, 19) is provided for   inside said cup (10), and in that a voltage is selected   applied between said intermediate electrode (12, 19) and said terminal electrodes (4a, 4b), so as to selectively   authorizing said bulbs (la, lb, lc) to emit light.   3. Fluorescent lamp according to claim 1 or 2, characterized in that each of said bulbs (la, lb, lc)   has a slot-shaped opening (3a, 3b, 3c).   4. Fluorescent lamp according to claim 3, character-   laughing at the fact that the openings (3a, 3b, 3c) of the bulbs (la, lb, lc) have different widths.   5. Fluorescent lamp according to claim 3, character-   in that the openings (3a, 3b, 3c) of the bulbs (la, lb, lc) are located in different positions in the direction circumferential of the bulbs.   6. Fluorescent lamp according to claim 1 or 2, characterized in that the phosphor coating layers (2a, 2b, 2c) deposited on the internal surfaces of the bulbs (la, lb, lc) are of mutually different types, and in that that the layers 2648 6 17   phosphor coating emit lights of different wavelengths.   7. Fluorescent lamp according to any one of the claims.   cations 1 to 6, characterized in that a sealing plate (9) having communication orifices (9a, 9b) and extending in a direction which intersects said discharge path (11) constituted by the bulbs and the base is provided in a connection part between the bulbs (la, lb, lc) and the base (10) constituting the discharge path (11), the interior of the bulbs is allowed to communicate with the interior of the base by the intermediate of said communication orifices, and the position of each communication orifice (9a, 9b) is moved away from the center of gravity of the cross section of each bulb towards the outside of   the curved area of said discharge path (11).   8. Fluorescent lamp according to any one of the claims.   cations 1 to 6, characterized in that each of said bulbs   (la, lb) has an oval cross section.